Distributing valve gear for steam engines



Patented Aug. 7, 1934 PATENT OFFICE DISTRIBUTING VALVE GEAR FOR STEAM ENGINES Hugo Lentz, Berlin, Germany Application July 7, 1931, Serial No. 549,246 In Germany July 15, 1930 4 Claims. (o1. 12 1 127) This invention relates to valve gear, in particular for use in connection with locomotive and marine steam engines. Steam engines for these purposes with valve gear in which all the inlet and exhaust valves are disposed in a single straight line, and in which the inlet valve stems are arranged within the hollow stems of the exhaust valves, are already known. The present invention relates to valve gear of this type, and has for its object to operate positively all four valves of each cylinder by means of a single actuating member, which is preferably in the nature of a roller lever but with fourfold action, to obtain a compact and yet easily accessible arrangement of the entire gear within a narrow casing or chest, to diminish the clearances, to obtain in a simple manner an equalization of pressure on both sides of the working piston when the engine is running idle, and also to effect the closing of the valves preferably by means of steam pressure applied to the valve stems. A further object of the invention is to render the gear suitable for very high speeds of rotation by means of a particular construction of the valves themselves and of the mechanism serving for the closing of thevalves.

The practical carrying out of the invention is illustrated in the accompanying drawing, in which:-

Fig. 1 is a fragmentary longitudinal sectional view taken parallel to the axis of the cylinder.

Fig. 2is a sectional view on the line cd of Fig. 1.

In the form of construction shown in Figs. 1 and 2 there is mounted on the cylinder 2 a valve gear chest 1 having in the middle a closed chamber 3 in which the actuating mechanism for the distributing valves is housed. The inlet valves 4 and the exhaust valves 6 are arranged symmetrically in relation to the chamber 3. The stem 5 of each inlet valve 4 is disposed within the hollow stem 7 of the corresponding exhaust valve 6, and the ends of all four valve stems 5, 7 project into the chamber 3.

The valves 4' and 6 are constructed with very thin walls, and are preferably made of sheet steel; instead of the so-called guiding cross, there is provided for each valve a disc 41 or 61 which is furnished with perforations or apertures and also forms the upper seating surface of the valve. The lower seating surface of each exhaust valve 6 cooperates with an inserted member 8 which is fitted into the chest 1, and which is adapted to serve as a guide for the hollow valve stem 7. This member 8 extends almost up to the valve disc 61,

means of a lever 171.

pins 20 to the base plate of the chamber 3.

so as to provide a good guide for the valve stem 7. For the guiding of the stem 5 of the inlet valve 4 there is provided an inserted member 9 the central bore of which is enlarged at 10 (Fig. l) to receive the end of the hollow stem 7. This inserted member 9 is likewise extended almost up to the valve disc 41. The stem 5 of each inlet valve 4 is further guided in a bore 11 in the cover 12 (Fig. 1), and this bore 11 is closed steam-tight at its outer end by means of a sleeve 28 screwed on the cover 12.

By means of a connecting piece 14 (Fig.1) steam is admitted into the bore 11, and exerts pressure upon the end of the stem 5 of the inlet valve 4, thus retaining the latterin the closed position. The inlet valve stem 5 is drilled longitudinally to form a passage 15 and transversely at 16 (Fig. 1), so that the steam admitted at 14 can also pass on into the space 10 (Fig. 1), and exerts presure on the end of the hollow stem 7, and thus also retains the exhaust valve 6 in the closed position. Saturated or wet steam is preferably employed for the closing of the valves, so that the stem 5 of the inlet valve 4, which is heated to a high temperature by the superheated working steam, is effectually cooled. Into the gear chamber 3 there is inserted a bushing 18 in which the oscillating lay shaft 17 is mounted (Fig. 2). In the constructional example shown the lay shaft 17 is caused to oscillate by On the end of the lay shaft 17 which projects into the chamber 3 there is provided a disc-shaped extension 172 with which there is formed in one piece the actuating member 19 adapted on being oscillated to operate all four valves. In the constructional example shown in Figs. 1 and 2 this actuating member 19 is constructed as a roller lever with fourfold action adapted to oscillate about its middle axis, and

takes the form, as shown in Fig. 1, of a narrow rib. The portions of the sides of the actuating roller lever 19 above the horizontal mid-line cooperate with two symmetrically disposing levers 22 on which are the counter rolling surfaces, and which are rotatably attached by means of These levers 22 are adapted to actuate with their free ends the ends of the stems 5 of the inlet valves 4. The portions of the sides of the actuating roller lever 19 below the horizontal mid-line cooperate in a similar manner with levers 23 which are attached by means of pins 21 to the base plate of the chamber 3, and which actuate with their free ends extensions 71 of the hollow stems 7 of the exhaust valves 6. The levers 22 and 23 will,

be referred to hereinafter as intermediate levers.

The ends of the intermediate levers 22 and 23 extend only as far as the middle axis of the valve stems 5 and '7, so that their ends do notoverlap. As can be seen from Fig. 1 the extensions of the solid stems 5 of the inlet valves have the lower part of their ends cut away in the manner of an arch, while the extensions 7' of the hollow stems 7 are cut away as to the upper part of their ends. In this manner the intermediate levers 22 are caused to act upon the inlet valve stems 5 only, and the intermediate levers 23, on the other hand, upon the hollow valve stems '7 only.

When the actuating roller lever 19 rocks as indicated by the double arrows in Fig. 1 its sides act with an initially small but very rapidly increasing arm of lever upon an initially large but very rapidly decreasing arm of the intermediate. levers 22 and 23. Since the cooperating surfaces of the actuating roller lever 19 on the one hand and of the intermediate levers 22 and 23 on the other hand carry out practically no sliding movement in relation to each other, no friction and therefore no appreciable wear takes place. As in the case of the known types of roller lever valve gear for stationary engines (always hitherto with simple and not multiple action of the roller levers) so also in the case of the present gear for locomotive and marine engines, which is required to be of very compact construction, a perfectly smooth opening and very rapid acceleration of the lift of the valves is obtained. Since the opening and closing of the valves is effected by roller .lever action, the periods of admission and compression are not subject to alterations through wear on the parts 19, 22, and 23 of the valve gear.-

The intermediate levers 22 serving for the actuation of the inlet valves 4 are provided, as will be seen from Figs. 1 and 2, with arms 24 directed towards the axis, that is to say towards each other, so that they overlap each other. Above the ends of these arms 24 there is arranged a 'stop or cam 26 which is attached eccentrically to the end of a shaft 25 rotatably mounted in the bush 18. In the position shown in Fig. 1 this stop 26 is without influence on the arms 24. If however the shaft 25 be rotated through 180, the stop 26 is brought into a lower position, and presses the arms 24 downwards (Fig. 1). The intermediate levers 22 are thereby pressed apart, so that they retain the inlet valves 4 permanently open. This arrangement serves to interconnect the portions of the cylinder on each side of the piston, and thus to effect an equalization of pressure on both sides of the piston when the engine is running idle, and

-in particular when the locomotive is running downhill.

It is to be noted that the inlet valves 4 are brought into the closed position not merely by steam pressure but also by the action of a helical spring 27. This spring 2'7 bears with its one end against the base of the sleeve 28. The other end of the spring 27 bears against the flange of a, sleeve 29. The base of this sleeve 29 acts upon a. pin 30 which is arranged-in an extension of the valve stem 5, and presses against the end of the valve stem 5. The steam admitted through the pipe 14 passes through channels 43 into the hollow space within the stem 5.

The live steam is admitted through the passages31 (Fig. 1) provided at the end of the chest 1, and passes through the inlet valves 4 into the cylinder ports 32 (Fig. 1), while the discharge steam passes through the exhaust valves 6 into the steam discharge space 33 (Fig. 1).

Through the described construction of the actuating member 19 for the actuation of all four valves of a cylinder as a roller lever with fourfold action, the employment of rollers is rendered entirely superfluous; in this manner a perfectly smooth and even running of the machine is obtained even at high speeds of rotation, and moreover the wear on the moving parts is reduced to a minimum. The rapid action of the gear is also furthered by the described particularly light construction of the valves, by the good bearing guides for the valve stems, and by the cooling of the inlet valve stems, particularly when the locomotive or marine engine embodying the present invention is operated with superheated steam.

I claim:-

1. In a valve gear for steam engines the combination with a cylinder, of a steam chest therer for, alined inlet and exhaust valves in the chest including stems slidably guided in the chest, the stems of the inlet valves having passages therein, means for conducting steam under pressure against the outer ends of the stems of the inlet valves and through the passages against the outer ends of the stems of the exhaust valves to seat the respective valves, and-means associated with the inner ends of the valve stems operable to unseat the valve.

2. In a valve gear for steam engines, the combination with a. cylinder, of a valve chest therefor, alined inlet and exhaust valves in the chest including mutually opposed stems, means for seating the inlet and exhaust valves, levers interposed between the valve stems and directly contactable therewith, a single oscillatory member between the inner ends of. the mutually opposed valve stems and directly engageable with all of the levers to actuate the levers to unseat the respective valves, the ends of the intermediate levers actuated by the actuating member extending only up to the longitudinal axis of the valve stems and the end of each of the valve stems being provided on the side furtherest removed from the intermediate lever pertaining thereto with a cut-away portion extending as far .as the axis of the stem.

3. Valve gear according to claim 1,- whereinmeans is provided for subjecting the inlet valve stems to an additional closing force which acts in the direction of the closing of the valves and includes a pressure pin the end of which acts upon the end of the inlet valve stem, and a spring acting on the pin.

4. Valve gear according to claim 1,- wherein the inlet and exhaust valves each include a disc attached to the valve stem and embodying one seating surface, and thin-walled valve body attached to the edge of said disc and embodying a second seating surface. HUGO LENTZ. 

